I’m currently battling it currently too from eggs I’ve hatched. It’s been extremely wet this spring. I’ve treated them twice already with toltrazuril and 2 days after their last dose they start back. I suspect mine have enteritis currently so they are on their second day of sulfa.
Sulfa can be purchased here. https://allbirdproducts.com/products/trimethoprim-sulfa-powder-generic
Here’s the toltrazuril https://allbirdproducts.com/products/endocox-powder
Both can also be purchased through Jedds.